Why won't my Nokia Lumia 810 update past OS Version 8.0.9905.12?

I have had this phone for almost two years now and after doing a factory reset a couple months ago I haven't been able to receive updates. I've gone into settings and manually checked for them multiple times, and the phone is set to automatically download when one becomes available- but it hasn't in a while. It's like the updates aren't reaching my phone. Also, extras +info won't update. I have turned everything off and back on, unblocked cookies on internet explorer, but every time it finishes the install it says there was an error. It doesn't give me an error code, just simply says if the download is an app to uninstall and reinstall it. Since extras and info isn't an app, there is nothing I can do.

My carrier is T-Mobile, and they no longer carry the Amber update. So, I'm thinking that's why I can't get past this old OS version. I've heard I can get the update through Nokia or Zune, but I'm kind of at a dead end as to HOW to do that. Any help would be appreciated.